The present invention relates to endoluminal vascular prosthesis deployment catheters, and in particular, to a deployment catheter for self-expanding straight segment or bifurcated prostheses for use in the treatment of abdominal aortic aneurysms.
An abdominal aortic aneurysm is a sac caused by an abnormal dilation of the wall of the aorta, a major artery of the body, as it passes through the abdomen. The abdomen is that portion of the body which lies between the thorax and the pelvis. It contains a cavity, known as the abdominal cavity, separated by the diaphragm from the thoracic cavity and lined with a serous membrane, the peritoneum. The aorta is the main trunk, or artery, from which the systemic arterial system proceeds. It arises from the left ventricle of the heart, passes upward, bends over and passes down through the thorax and through the abdomen to about the level of the fourth lumbar vertebra, where it divides into the two common iliac arteries.
The aneurysm usually arises in the infrarenal portion of the diseased aorta, for example, below the kidneys. When left untreated, the aneurysm may eventually cause rupture of the sac with ensuing fatal hemorrhaging in a very short time. High mortality associated with the rupture led initially to transabdominal surgical repair of abdominal aortic aneurysms. Surgery involving the abdominal wall, however, is a major undertaking with associated high risks. There is considerable mortality and morbidity associated with this magnitude of surgical intervention, which in essence involves replacing the diseased and aneurysmal segment of blood vessel with a prosthetic device which typically is a synthetic tube, or graft, usually fabricated of Polyester, Urethane, DACRON(copyright), TEFLON(copyright), or other suitable material.
To perform the surgical procedure requires exposure of the aorta through an abdominal incision which can extend from the rib cage to the pubis. The aorta must be closed both above and below the aneurysm, so that the aneurysm can then be opened and the thrombus, or blood clot, and arteriosclerotic debris removed. Small arterial branches from the back wall of the aorta are tied off. The DACRON(copyright) tube, or graft, of approximately the same size of the normal aorta is sutured in place, thereby replacing the aneurysm. Blood flow is then reestablished through the graft. It is necessary to move the intestines in order to get to the back wall of the abdomen prior to clamping off the aorta.
If the surgery is performed prior to rupturing of the abdominal aortic aneurysm, the survival rate of treated patients is markedly higher than if the surgery is performed after the aneurysm ruptures, although the mortality rate is still quite high. If the surgery is performed prior to the aneurysm rupturing, the mortality rate is typically slightly less than 10%. Conventional surgery performed after the rupture of the aneurysm is significantly higher, one study reporting a mortality rate of 66.5%. Although abdominal aortic aneurysms can be detected from routine examinations, the patient does not experience any pain from the condition. Thus, if the patient is not receiving routine examinations, it is possible that the aneurysm will progress to the rupture stage, wherein the mortality rates are significantly higher.
Disadvantages associated with the conventional, prior art surgery, in addition to the high mortality rate include the extended recovery period associated with such surgery; difficulties in suturing the graft, or tube, to the aorta; the loss of the existing aorta wall and thrombosis to support and reinforce the graft; the unsuitability of the surgery for many patients having abdominal aortic aneurysms; and the problems associated with performing the surgery on an emergency basis after the aneurysm has ruptured. A patient can expect to spend from one to two weeks in the hospital after the surgery, a major portion of which is spent in the intensive care unit, and a convalescence period at home from two to three months, particularly if the patient has other illnesses such as heart, lung, liver, and/or kidney disease, in which case the hospital stay is also lengthened. The graft must be secured, or sutured, to the remaining portion of the aorta, which may be difficult to perform because of the thrombosis present on the remaining portion of the aorta. Moreover, the remaining portion of the aorta wall is frequently friable, or easily crumbled.
Since many patients having abdominal aortic aneurysms have other chronic illnesses, such as heart, lung, liver, and/or kidney disease, coupled with the fact that many of these patients are older, the average age being approximately 67 years old, these patients are not ideal candidates for such major surgery.
More recently, a significantly less invasive clinical approach to aneurysm repair, known as endovascular grafting, has been developed. Parodi, et al. provide one of the first clinical descriptions of this therapy. Parodi, J. C., et al., xe2x80x9cTransfemoral Intraluminal Graft Implantation for Abdominal Aortic Aneurysms,xe2x80x9d 5 Annals of Vascular Surgery 491 (1991). Endovascular grafting involves the transluminal placement of a prosthetic arterial graft within the lumen of the artery.
In general, transluminally implantable prostheses adapted for use in the abdominal aorta comprise a tubular wire cage surrounded by a tubular PTFE or Dacron sleeve. Both balloon expandable and self expandable support structures have been proposed. Endovascular grafts adapted to treat both straight segment and bifurcation aneurysms have also been proposed.
Notwithstanding the foregoing, there remains a need for a structurally simple, easily deployable transluminally implantable endovascular prosthesis, with a support structure adaptable to span either a straight or bifurcated abdominal aortic aneurysm. Preferably, the tubular prosthesis can be self expanded at the site to treat the abdominal aortic aneurysm, and exhibits flexibility to accommodate nonlinear anatomies and normal anatomical movement.
There is provided in accordance with one aspect of the present invention, an endoluminal graft deployment catheter. The catheter comprises a proximal outer tube section, having a proximal end and a distal end, and an intermediate tube extending through the proximal tube section and beyond the distal end. A central core extends through the intermediate tube, and a cap is attached to the central core. The central core is rotationally linked to the intermediate tube.
Preferably, the intermediate tube is rotationally linked to the outer tube. The cap is axially movable between a first position in which it contacts the outer tube and a second position in which it is spaced distally apart from the outer tube, such as to deploy an entrapped prosthesis.
The central core preferably comprises a flexible tube. In one embodiment, the tube comprises a polymeric braid. One suitable polymer is polyimide.
In accordance with a further aspect of the present invention, the central core further comprises a reinforcing element which, overlaps the point of contact between the cap and the outer tube. In one embodiment, the reinforcing element comprises a tubular structure carried by the flexible central core.
In accordance with a further aspect of the present invention, there is provided an endoluminal graft deployment catheter. The catheter comprises an elongate flexible body, having a proximal end and a distal end. A proximal outer tube section has a proximal end and a distal end, and a distal outer tube section has a proximal end and a distal end. The proximal outer tube section is rotationally linked to the distal outer tube section, and a central core extends through the proximal end distal outer tube sections. The proximal and distal tube sections define a prosthesis cavity therein for carrying a prosthesis, and axial separation of the proximal tube section from the distal tube section opens the cavity to release the prosthesis.
In one embodiment, each of the proximal tube section and distal tube section is rotationally linked to the central core. At least one of the proximal tube section and distal tube section is axially movable between a first position in which the cavity is closed and a second position in which the cavity is open. The proximal tube section and distal tube section thus form a junction when in the first position, and the catheter preferably further comprises a reinforcing element which spans the junction. In one embodiment, the reinforcing element comprises a tube for surrounding the central core.
Further features and advantages of the present invention will become apparent to those of ordinary skill in the art in view of the disclosure herein, when considered together with the attached drawings and claims.